"range extending" gasoline powered internal combustion engine (ICE) as a genset and therefore dubbed the Volt an "Extended Range Electric Vehicle" or E-REV. In a January 2011 interview, the Chevy Volt's Global Chief Engineer, Pamela Fletcher, referred to the Volt as "an electric car with extended range." The Volt operates as a purely electric car for the first in charge-depleting mode. When the battery capacity drops below a pre-established threshold from full charge, the vehicle enters charge-sustaining mode, and the Volt's control system will select the most optimally efficient drive mode to improve performance and boost high-speed efficiency. According to General Motors' real time tally of the distance driven by Volt owners in North America, by mid June 2014 they had accumulated more than . GM also reported that Volt owners driving is more than 63% in all-electric mode. Volt owners who charge regularly typically drive more than between fill-ups and visit the gasoline station less than once a month. A similar report, issued by GM in August 2016, reported that Volt owners have accumulated almost driven in EV mode, representing 60% of their total distance traveled. BMW i3 The BMW i3 all-electric car with at least 22 kWh battery capacity offers an optional gasoline-powered range extender APU. The range extender is the same 647 cc two-cylinder gasoline engine used in the BMW C650 GT scooter with a fuel tank. The US model originally had its tank electronically limited to a smaller 7 L capacity. The range extender engages when the battery level drops to 6%. It generates electricity to extend the range from to Performance in range-extending mode may be more limited than when it is running on battery power, as BMW designed the range extender as a backup to enable reaching a recharging location. According to BMW, at the beginning of the i3 release, the use of range-extender was much more than the carmaker expected, more than 60%. Over time it has decreased significantly, with some people almost never using it, and by 2016 it is being regularly used in fewer than 5% of i3s. The range-extender option costs an additional in the United States, an additional (~ ) in France, and (~ ) in the Netherlands. The range-extender option of the BMW i3 was designed to meet the CARB regulation for an auxiliary power unit (APU) called REx. According to rules CARB adopted in March 2012, the